I have; they are supposed to help with bigger litters. I know I see rabbits in my gravel drive picking up pebbles that I assume have salt from snow residue on them. I think it's hard for them to find salt in most habitats.

I been using the Sulfa/salt block for years they did some studies over at UGA, a number of years ago, and they reported that the Sulfa in the Salt blocks were lot, better for wild life,, it sure has help my wildlife here on this property,I Keep them inside my Starting pens. all the time..

I put sulfa salt in my running pen and had 6 rabbits in it when I stopped running my dogs in April. I have trapped and released 8 rabbits in the last two days! Probably still 45 or 50 more to release before the count is down enough to put dogs back in my enclosure! I attribute the numbers, at least partially, to the salt.

DNR had a study done and that what it showed healthy bigger litters an helps with the worms ,I did it to a 15 acre Gravel pit with the brown salt blocks took a hammer an broke it in smaller pieces an put it every where,in the snow I had 5 rabbits go by me an then the one the dogs were running